Crossbar-switch selector system



Oct. 23, 1956 R. w. HUT'roN cRossEAR-swITcH SELECTOR SYSTEM 4 sheets-sheet 1 Filed Dec. 2l, 1954 Oct. 23, 1956 R. w. HUTToN 2,768,241

CROSSBAR-SWITCH SELECTOR SYSTEM Filed Deo. 2l, 1954 4 Sheets-Sheet 2 Oct.A 23, 1956 R. w. Hur'roN 2,763,241

cRossBAR-swITcH"SELECTOR SYSTEM Filed Dec. 21, 1954 4 sheets-sheet 5 N E .N .mi

Oct 23, 1956 R. w. HUTToN cRossBAR-swITcH SELECTOR SYSTEM 4 Sheets-Sheet 4 Filed Dec. 21, 1954 NwN o wm. o wm. o wm. 2..: lll

United States Patent CROSSBAR-SWIT CH SELECTOR SYSTEM Robert W. Hutton, Chicago, lll., assignorto International Telephone and Telegraph Corporation, New York, N. Y., a corporation of Maryland Application December 21, 1954, Serial No. 47 6,747

6 Claims. (Cl. 179-22) This invention relates generally to a crossbar-switch selector system but is concerned more particularly with a selector system of that type wherein the trunks incoming to the selector stage lare given direct access, as distinct from link access, to the trunks outgoing from the selector stage. Its principal object is to provide a new andimproved switchboard arrangement of standaridized crossbar switches to comprise economical groups, or shelves, of selector switches which may be mounted in tiers or frames requiring a minimum of lloor space.

In direct-access crossbar selector systems, as shown for example in the United States patent application of R. W. Hutton et al. for a Multi-Group Direct-Access Crossbar Telephone Switching System, Serial No. 359,761, vfiled .lune 5, 1953, it is common practice to employ a separate tier or shelf of standardized crossbar switches for eachv group of in-trunks to give them ten-trunk access to each of ten separatelvdesignated numerical groups, or levels, of out-trunks. switches may comprise a shelf serving a group of twelve in-trunks connected in common to the horizontals of all live switches. Each such switch accordingly'h'as twelve horizontals, and each switch gives the twelve in-t'runks ten-trunk access to each of two levels of out-trunks by having twenty verticals arranged in two selectable groups corresponding to respective levels of out-trunks.

The foregoing arrangement of cross bar switches for direct-access systems has been used satisfactorily in exchanges having ample floor space but due to the large number of shelves of switches required, has not been considered feasible in exchanges wherein oor space is at a premium.

According to the invention, advantage is taken of the known techniques of increasing the capacity of standardized crossbar switches, comprising (l) arranging each switch in two sections with separate verticals and horizontals, and (2) electively doubling the horizontals of a section byv arranging that each physical horizontal comprises two alternative trunk paths. may then comprise twelve verticals each having access to twenty horizontal paths. By connecting in-trunks to the twelve verticals of Such a section and connecting outtrunks to the twenty horizontal paths thereof, each section of such a two-section switch can be replace an entire switch of the cited application by `giving twelve in-trunks ten-trunk access to each of two levels.

In a preferred embodiment, the first section of each of five switches of a shelf give a first group of twelve intrunks ten-trunk access to the ten levels of ou-t-trunks, with the second section of the live switches similarly serving a second group of twelve in-trunks.

In a second embodiment, the five sections comprising the first two and a half switches serve the lrst group of in-trunks, while the remaining sections of the shelf serve the second group of in-trunks.

The control over the switches of a shelf is preferably exercised by a shelf controller generally as disclosed in In the cited application, tive crossbar Each section of a switchl 2,768,241 Patented Oct. 23, 1956 f. ICC

Fig. l shows diagrammatically the two-section switchesy and the associated apparatus of a selector shelf serving two groups of in-trunks according to the noted preferred embodiment;

Fig. 2 shows in circuit diagram the esssential circuit details of the apparatus of Fig. 1; and

Fig. 3 shows the apparatus of Fig. 1 arranged according to the noted second embodiment of the invention.

GENERAL OPERATION Referring now to Fig. 1 of the drawings, a tier or shelf of selector switches and the asociated control apparatus is shown, comprising five two-section switches SW1 to SWS of which only the first and last are shown; two groups of selector units SELl to SELIZ and SEL13 to SEL24; and an associated shelf controller SCI common to switches SW1 to SWS. The switches of the disclosed shelf are shown arranged side by side but may be mounted one above another on aten or twenty switch frame.

Each of the disclosed switches SW1 to SWS is similar to those disclosed in United States Patent No; 2,577,067

I issued December 4, 1951, to R. P. Arthur for a Crossbar the cited application, but rearranged to preside over two Switch. In such a switch, it is well-known that severing the horizontal multiple between any two adjacent verticals provides two similar groups of horizontal multiples with each group having the original number of termination points and being accessible by a portion of the original number of verticals. The number of verticals having access to each horizontal multiple group being determined by the adjacent verticals selected as the point for severing the horizontal multiple.

In this disclosure7 the horizontal multiple of a 25 x 20 switch (25 verticals and 20 horizontals) is severed between the twelfth and thirteenth verticals, thereby eiectively providing two similar l2 x 20 switch sections.

Referring now to Fig. l, it has been chosen to group the selector units into two groups of twelve selector units each, with the selector units of one group being connected to respective verticals 1 to l2 of the first section of each of the tive switches and the selector units of the other group being connected to respective verticals 13 to 24 of the second section of each of such switches.

In any switch section, the twenty horizontals, comprising ten upper paths and ten lower paths, are divided into two groups of ten paths each and are assigned trunks in respective levels. For example, the rst ten horizontal paths (upper and lower horizontals l to 5) of switch SW1 are assigned to respective trunks in the level 1 group of trunks and the second ten horizontals of the same section (upper and lower horizontals 6 to 10) are assigned to respective trunks in the level 2 groups of trunks. The twenty horizontals of section l of switch SW2 are connected to trunks in levels 3 and 4 and so forth with switch SWS being associated with trunks in levels 9 and 10.

In Fig. l, selectors SEL1 to SEL12 to comprise a rst group of 12 selectors and are connected to respective verticals 1 to 12 of section 1 of switch SW1 by conductors in cable group 101, and are further multipled to re' spective verticals of section 1 of each of the switches SW2 to SWS by conductors in cable groups 102 to 105, respectively. Selectors SEL13 to SEL25, comprising a second group of 12 selectors, are connected lto respecspective groups by conductors in cable groups 151 to 170 and are terminated on an intermediate distributing Aframe by conductors in cable group 1261.

The switches SW1 to SWS are dividediinto two sections as noted, with the left-hand section being termed section 1 and the right-hand section being termed section 2. Horizontal pairs 1 to 5 are termed horizontal groups 1 or lower group of horizontals and horizontalpairs 6 to are termed horizontal group 2 or the upper group of horizontals, respectively. Accordingly, as observed inV Fig. l, the level 1 trunks of section 1 of switch SW1 are -terminated on the rst or lower groups of horizontals of such section and the level 2 trunks thereof ,areterminated on the second or upper group of horizontals. The selectors SELI to SEL12 are termed selector group 1 or the rst group and selectors SEL13 to SEL24 are termed selector group 2 or the second group of selectors. The following table shows the trunk level assignment to respective sections of respective switches and shows the selector groups having access thereto.

Figure-1 table Section In the foregoing table, the Group heading refers to the horizontal group and the numeral 1 refers to the first or lower group while the numeral 2 refers to the second or upper group of horizontals.

Cable 1261 includes conductors from other selector shelvesand are terminated on the intermediate distributing frame from whence they may be graded and multipled in the manner exemplied by United StatesPatent No. 1,633,118issued June 21, 1927, to H. B. McElyea for a Bank and Trunk Cabling System.

A shelfcontroller CR1 is provided for each shelfof selectors andis associated with the switches therein by conductors in cablegroups 121,to 124 and is also associated with the two groups of selectors by conductors in cable group 131.

Responsive to the well-known extension of a connection from a calling line through Athe associated line switch to an idle selector, the concerned selector records an indication of the level called and calls-in the shelf controller over conduc-tors in cable 131. As is usual in a system having common control equipment, the shelf controller is individualized with the calling selector and responds to the recorded information to control the switch and switch section serving the called level to make connection withk an idle trunk inthe calledlevel. The detailed operation of the shelf controller in controlling the switches SW1 to SWS will be described hereinafter. Responsive .to the connection of the calling selector with yan idle trunk in the called level, the shelf controller is returned to common use in preparation for handling calls from other selectors.

4 DETAILED DESCRIPTION Referring now to Fig. 2 of the drawings, a detailed description of shelf controller SCI, in controlling switches SW1 to SWS in extending connections from calling ones of the two groups of twelve selectors to idle trunks in a called level of trunks, will now be given.

Fig. 2, parts 1 to 3, disclosesA a fragmentary circuit diagram of a selector SELl connected by tip, ring and sleeve conductors T, R, and S of cable 101-1 to vertical V1 of crossbar switch SW1 andfconnected by conductors in cable group 131-to cable C191 extending to shelf controller SCI. The shelf controller SCI, common to both selector groups, is shown in circuit detail and is arranged to respond to control from any selector of the noted groups to control swi-tches SW1 toV SWS to ex-tend a connection from a calling selector to an idle connector, such as connector CONN-1, by way of an idle trunk.

The S7 relays of shelf. controller SCI has principal functionsx assigned thereto as follows:

Relays,2tl1 to 210 (hold-magnet call-in relays) are grouped into ve groups of two. relays each, with each group being associated with a crossbar switch of the selectorshelf to control the operate -leads of the hold magnets therein, the relays of each group corresponding respectively/.to the sections ofthe associated switch;

Relays 211 to.215 (select-magnet call-in relays) are associated respectively with the ve switches of the shelf, and when operated, associate the operate windings of the select magnets (10 principal and 2 extensions) to the shelf controller;

Relays 216- yto 235 (trunk-test relays) corespond respectively to the 20 trunks serving a switch section. Relays,.216 to 225 are associated with the first group or lower group of horizontal paths and relays 226 -to 23S are associated with the second group of horizontals. These relays operate to determine the busy or idle condition of such trunks connected to associated horizontals;

Relays 236 and 237 (cutoff relays) are connected in parallel and operate `to disable the testing circuit of the trunks responsive -to the selection of an idle one in the called group; and

Relays 238 to 257 (idle-test call-in relays) `are grouped into tive groups of four relays each, with each group of four relays being associated with a separate switch. rI'he first relay of each group call-in the trunks associated with the first or lower group 'of horizontals of the first section of -its associated switch; `the second relay corresponds 'to the upper group of |horizontals lof the same section; the third relay corresponds to the lower horizontals of the second section `of its associated switch, and so forth. These relays .accordingly cooperate with the trunk-test relays in selecting :an idle trunk in the called numerical group lor level.

Responsive to a calling condi-tion on the trunk extending ito selector SEL1, by the closure of Ithe calling loop across the tip and ring conductors incoming thereto, the calling subscriber dials the digit corresponding to the level tof trunks desired, Isuch digit being recorded in selector SELL For purposes of clarity, it has been `chosen to assign the digits of the called number to Irespective levels, that is, level 1 corresponds 'to the digit 1 and so forth.

In `the well-known manner, `a digit register DR is 'advanced across lthe bank wires 'of the register in yaccordance with the value `ot" the digit dialed Iand becomes positioned ion thewi-re corresponding to the recorded digit. Following such dialing, :selector SELl, by circuit `details not shown, becomes individualized with shelf controller SCI'. At the `same time, as indicated in the drawings, the control wire SMOP is grounded 'and the control wires SON 'and HMOPI are connected together.

For purposes of illustrati-on, it has been chosen to assume the digit 1 to be dialed in `selector SELl Iand group control wire GCI to be grounded by the operation of the digitlsregis'ter DR.

lleierring in particular to selector SL, itbein-g a selector in the first 'selector group, it will be observed that the group control wires `GC1 to GC10, corresponding to digits 1 to 0, are multipled as indicated. This multipling, however, is among the selectors of its .associated group, selectors SELZ Ito SEL12. Another set of group control wires GC11 to GC24, corresponding respectively to digit 1 to O, are provided tor the selectors SEL13 to SEL24 and are separate lfrom the group control wires of the rst group of selectors. This is illustrated in the lower portion of Fig. 2, part 3, where the two sets of control wires are connected to jumper board J B267 Ground ion the group control wire GC1 is extended over the group control wire in cable C191 to the jumper board J B267 of controller SCI.

yReferring now to jumper hoard J B267, it vwill be observed -that two sets of group control wires are terminated thereon, these two groups comprising group control Wires GC1 to GC1() and GC11 to GO20, las previously noted. With the twenty idle-test call-in relays being grouped into live groups vof four relays each, as previously noted, and with each relay of a group being associated with a separate set of ten horizontals which respectively terminate trunks of associated levels, the group control Wire grounded responsive to the calling of la desired level must be connected to the idle-test relay associated with the trunks in the called level which are accessible by the calling selector group. In accordance with the Fig. 1 table, group control wire GC1, corresponding to the trunk level 1 served by the lower group Iof horizontals of section 1 of switch SW1 is connected by jumper 270 to idle-test relay 238, such relay being associated with the lower group of horizontals of the tirst section of switch SW1. Y

Likewise, group control Wire GC2 corresponding to the called digit 2 and .trunk level 2, is jumpered by means of jumper 271 to the battery-connected winding of relay 239, to call-in for test the trunks connected to the upper group of horizontals of lsection 1 of switch 1 responsive to dialing of level 2 trunks.

Responsive to a call from the second group of selectors, the corresponding one of the group control Wires GC11 to GC20 is grounded in accordance with the digit dialed and the group control Wires are jumpered to the associated call-in relay in a Isimilar manner. Accordingly, group control wire GC11, Icorresponding to the digit 1 :and -level 1, is jumpered by jumper 280 to the batteryconnected winding of idle-test call-in relay 240 to call-in for test the trunks connected to the lower group of horizontals of :section 2 of switch SW1, such trunks being accessible by the `second group of selectors.

Responsive Ito the grounding 'of group-control wire GC1 as hereinbefore noted, idle -test call-in relay 238 operates and at its contacts 1 to 10 calls-in the sleeve wires of .the trunks associated with such horizontals. These sleeve extension wires are extended over corresponding conductors 1 to 10 in cable group 262 to the upper winding of respective 4trunk-test relays 216 to 225 of Fig. 2, part 2.

In the levent that group control wire GC2 was grounded, relay 239 would operate :and connect the sleeve extension wires associated with the level 2 trunks to the upper winding of respective trunk test relays 226 to 235.

Ground potential trom contacts 1 to 10 of each of the cutot relays 236 and 237 .appears on the others side of the upper winding of each trunk test relay, completing an operate circuit for the test relays associated with theidle trunks and Ishunting such ywinding of the relays associated with busy trunks.

Assuming the first live trunks extending to the connectors such ias connector CONN-4, to be idle, fand the remaining ve trunks in the called level to be busy, idleindicating battery potential appearing on the sleeves of the idle trunks, such `as from resistor 268 of connector CONN-1, Vappears on one side of the upper winding of the rst live relays of relays 216 to 225 and ground potential on the sleeves of the busy trunks appear on th" busy. Each of the five Ioperated relays :at their make' lirst contacts 4 tries to lock operated to ground potential on wire 263, grounded lat contacts 11 vof relay 238. Since relay 216 has the operating preference as determined by' its contacts S, it is the only relay to lock operated as its contacts 5 disconnects locking ground from the remainder of the relays. p

Make contacts 6 of the operated trunk-test relay 216 entends ground potential to the battery-connected winding of relays 236 land 237 causing them to operate and remove ground potential from one side fof the .test winding :of all the trunk-test relays, permitting all relays to restore, except the one locked operated through its make contacts 4.

Responsive to the hereinbefore described operation of idle test call-in relay 238, make contacts 12 and 13 thereon extend ground potential over wire 265 and over conductor 1 of cable 266 to the battery-connected winding of select magnet call-in relay 211 and to the battery-connected winding of hold magnet call-in relay 201. Relays 201 and 211 thereupon operate.

At such time, idle-test call-in relay 238, trunk-test relay 216, cutoif relays 236 and 237, select magnet call-in relay 211, and hold magnet call-in relay 201 are operated.

As noted, the hold magnet call-in relays select the switch section to which the calling selector is associated, the select magnet call-in relays select the switch containing the horizontals serving the called level; and the idle-test call-in relay selects the group of horizontals serving such level. From these three relays, the shelf controller is individualized with the switch, the switch section and the horizontal group containing the called trunk level, For complete selection, the controller has yet to identify an idle trunk in such level.

Referring now in particular to the trunk test relays, it will be observed that each pair of relays is associated with a separate select magnet control wire, and that each relay of a pair is associated with a separate extension magnet wire.

Accordingly, each of the test trunk relays when operated, performs a dual purpose by identifying the horizontal pair corresponding to the selected idle trunk and by selecting the upper or lower path corresponding thereto. With such information, the shelf controller SCI is prepared to operate the switch to effect the extension of a connection from a calling selector to an idle trunk in a called level.

Responsive to the operation of trunk-test relay 216, the ground on select magnet Operate Wire SMOP is extended through make contacts 2 and 3 to the select magnet control wires SMC1 and SMCU. This ground is extended through contacts 1 and 11 of relay 211 to the battery-connected Winding of principal select magnet SM1 and the winding of extension select magnet SMU of switch SW1, as determined by the operation of relay 211.

Select magnets SMU and SM1 operate and at their olfnormal contacts, ground the secondary olf-normal wire SON and mechanically selects the horizontal pair and the upper and lower horizontal therein corresponding to the selected trunk.

-As hereinbefore noted, the secondary oft-normal Wire SON is connected to the hold magnet operate wire HMOP, such hold magnet operate Wire being individual to selector SEL1, and the ground thereon now appears on-the hold magnet operate wire HMOPI.

Responsive to the hereinbefore noted operation of the hold magnet call-in relay 201, its make contacts 1 extend the ground on the hold magnet operate wire HMOPI to the associated hold magnet HMI of the switch SW1 to cause thehold magnet therein to operate, thereby connectingthe tip, ring, and sleeve conductors of selector SELI to respective tip, ring, and sleeve conductors of the selected trunk connected to connector CONN1. The operate ground on the hold magnet HMI is extended through'its off-normal contacts to the sleeve conductor S of the selected trunk to operate the usual switch-through relay (not shown) in selector SELI and to project a ground forward to maintain the selected trunk busy to other calls to trunks in that level.

At such time, responsive to the operation of the cutthrough relay of the selector, ground is removed from the digit Wires, and from the select magnet operate Wire SMOP, and the connection between the secondary offnormal Wire SON and the hold magnet operate wire HMOPI is opened, thereby permitting the idle test call-in relays and the select magnets to restore. Responsive -to the restoration of the idle-test relay, the operated trunktest relays, the operated hold-magnet call-in relay and the operated select-magnet call-in relays are restored, returning the shelf controller SCI to common use again.

At such time the connection from the calling selector SELI to the idle connector CONN-I associated with the selected trunk is complete and the calling subscriber dials the remaining7 digits of the directory number in the usual manner to extend a connection to the called-line.

Referring again to the idle-test call-in relays 238 to 257, the operation of shelf controller SCI has been described with reference to the trunk levels comprising ten trunks. Shelf controller SCI may be arranged for handling twenty trunks in a group such as might arise in the event that the twenty trunks connected to the horizontals of either sections of a switch may be grouped in one level. In such an arrangement, the group control wire associated with the called level would be jumpered to Ytwo idle test call-in relays, each relay calling-in ten trunks.

For example, assuming section I of switch SW1 serves twenty trunks in level I, the group control wire GCI, corresponding to level I would be jumpered to idle-test call-in relays 238 and 239. In such an event, all twenty trunk-test relays 216 to 235 would simultaneously test the associated trunks.

SECOND EMBODIMENT Referring now to Fig. 3 of the drawings, a second embodiment of the invention will be described.

In Fig. 3, switches SWII and SWI3, comparable to switches SW1 to SW3 of Fig. l, are shown in block diagrams with the groups of horizontals of each section being indicated as levels. For example, the lower horizontal group of section I of switch SW1 is designated level I, the upper group being designated level 2, and so forth.

The purpose of this embodiment is to illustrate another of the numerous ways in which the selector groups might be assigned to the various switch sections and in which the trunk levels might be grouped.

In Fig. 3, the tirst group of selectors, selectors SELI to SELIZ, are connected to the verticals of the live sections of the first two and one half switches by conductors in cables 301 to 305 and the second group of selectors, selectors SELS to SEL24, are connected to the verticals of the ve sections of the remaining switches by conductors in cables 311 to 315, cables 313 to 315 not shown.

Shelf controller SCI is arranged to handle the rearranged selector groups by the assignment of group control wires to associated idle-test call-in relays so that the trunks called-in correspond to the level called, in a manner similar to that described with reference to the lrst embodiment of the invention.

I claim:

1. In a switching system, selector switching apparatus of crossbar switches each including two sections andl having select magnets common to both sections, each section including a separate group of horizontal multiples corresponding respectively to the common select magnets andincluding a set of vertical multiples intersecting the associated horizontal multiples, each section further including hold magnets and associated crosspoint means for connecting any horizontal multiple of the section to any vertical multiple thereof under the joint control of the hold magnets of the section andthe common select magnets, a group of irl-trunks comprising trunks connected respectively to verticals of each of a selected number of the said sections, the group ofhori'- zontall multiples of any lastsaid section comprising subgroups, the groups of out-trunks comprising separately designated numerical groups, or levels, each said subgroup of horizontal multiples being -assigned to a separate said level, wiring means connecting trunks of any said level to respective horizontal multiples in the said subgroup of horizontal multiples assigned to such level, means controlled over 4any calling one of the in-trunks in the said group thereof for designating any said level as a called level, means responsive thereto for selecting an idle trunk of the called level appearing in the corresponding assigned one of said subgroups of horizontal multiples, means for controlling the select magnets of the switch containing the section in which the last said subgroup of horizontal multiples is located to select the horizontal multiple therein to which the said selected trunk is connected, means for opera-ting a hold magnet of the last said section to control `associated crosspoint means to connect the calling in-trunk to the said selected out-trunk in the called group by way of the said selected horizontal multiple.

2. A switching system according to claim 1, wherein the said two sections of at least one crossbar switch terminate separate respective groups of in-trunks, whereby that switch provides two outlet levels for each of two groups of in-trunks.

3. A switching system according to claim l, wherein the said two sections of each crossbar switch of a group terminate `separate respective groups of in-trunks, whereby each such switch provides two outlet levels for each of two groups of in-'trunks 4. A switching system according to claim 1, wherein the two sections of at least one said crossbar switch terminate separate respective groups of in-trunks, and wherein the two sections of any other said crossbar switch each terminates a single group of in-trunks and provides that group with access to four levels of out-trunks.'

5. A switching' system according to claim l, wherein the two sections of any said crossbar switch terminate the same groupV of in-trunks and provides that group with access to four levels of out-trunks.

6. In a switching system according to claim l, wherein at least one section not included in the said selected number of sections has its horizontal multiples in one large group corersponding to a single level of out-trunks, means responsive to the designation of the last said level for selecting `an idle trunk connected to any last said horizontal multiple, and means for operating a hold magnet of the last said section to control associated crosspoint means to connect the calling in-trunk to the said selected out-trunk in the called group by way of the said selected horizontal multiple.

No references cited. 

